1. Field of the Invention
The present invention pertains to safety penetrating instruments and, more particularly, to automatic safety penetrating instruments having outer sleeves for introduction into anatomical cavities and penetrating members within the outer sleeves with sharp tips for penetrating cavity walls.
2. discussion of the Prior Art
Penetrating instruments are widely used in medical procedures to gain access to anatomical cavities ranging in size from the abdomen to small blood vessels, such as veins and arteries, epidural, plueral and subarachnoid spaces, heart ventricle and spinal and synovial cavities, with access being established via an outer sleeve or cannula positioned during penetration into the cavity with the penetrating instrument. Such penetrating instruments include a penetrating member having a sharp tip or point to pierce or penetrate the tissue forming the cavity wall, and the force required to penetrate the cavity wall is dependent upon the type and thickness of the tissue of the wall. Once the wall is penetrated, it is desirable to prevent the sharp tip of the penetrating member from inadvertent contact with or injury to tissue or organ structures in or forming the cavity, and a particular problem exists where substantial force is required to penetrate the cavity wall or the cavity is very small in that, once penetration is achieved, the lack of tissue resistance can result in the sharp tip traveling too far into the cavity and injuring adjacent tissue or organ structures.
Safety penetrating instruments including a safety probe biased to extend beyond the sharp tip of a penetrating member have become widely accepted for use in penetrating anatomical cavities. For example, the Verres needle, commonly used to create a pneumoperitoneum, has a spring-loaded inner member disposed within a tubular needle. U.S. Pat. No. 1,527,291 to Zorraquin, No. 2,623,521 to Shaw and No. 2,630,803 to Baran are exemplary of safety penetrating instruments with a spring-loaded inner member disposed in a needle, while U.S. Pat. No. 4,254,762 to Yoon shows an endoscope spring-biased in a hollow needle. German Offengulaschrift 2,544,262 discloses an intrauterine catheter including a tube having a distal sharp point, a spring-biased blunt member in the tube distal end and a hose or catheter slidable over the tube.
Safety trocars having a spring-biased protective shield disposed between an outer sleeve and an inner trocar are marketed by Ethicon, Inc. as the Endopath and by United States Surgical Corp. as the Surgiport. U.S. Pat. No. 4,535,773 to Yoon, No. 4,601,710 to Moll and No. 4,654,030 to Moll et al are illustrative of such safety trocars. A trocar disposed within a portal sleeve and retractable within the sleeve in response to an electrical signal generated when force from tissue contact is removed from the sharp tip of the trocar is set forth in U.S. Pat. No. 4,535,773 to Yoon.
One of the limitations of many prior art safety penetrating instruments is that the safety probes can produce an irregular surface or profile with the sharp tips of the penetrating members during penetration of tissue resulting in increased resistance during penetration of a cavity wall, trauma and damage to tissue and possible jamming and trapping of tissue. Another limitation of many prior art safety penetrating instruments is that very small or narrow anatomical cavities cannot be penetrated without protrusion of the safety probes or shields from the sharp tips of the penetrating members. A further limitation of many prior art penetrating instruments is that the penetrating members cannot be automatically retracted, with or without the safety probes or shields within the outer sleeves upon penetration into an anatomical cavity. Many prior art penetrating instruments are also limited in that the penetrating members cannot be automatically retracted to safe, protected positions wherein the sharp tips of the penetrating members are disposed within the instruments upon penetration into anatomical cavities and thereafter selectively moved to various extended positions with the sharp tips protruding into the cavities for performing various surgical procedures. Many prior art safety penetrating instruments are also limited in that the instruments cannot be automatically held, anchored or stabilized within the anatomical cavities upon penetration therein or selectively anchored where automatic stabilization is not desired.